WASHINGTON (CNN) -- President Bush's top adviser on homeland security is stepping down after 4½ years on the job, the White House said Monday.

Fran Townsend served more than four years as homeland security adviser.

Homeland Security Adviser Fran Townsend turned in her letter of resignation to President Bush on November 6 and will be looking for new opportunities outside government.

"I'm going to just take another job doing 20-hour days, but this time in the private sector," said Townsend, who has spent 25 years working in law enforcement and government.

Bush praised Townsend's work Monday.

"Fran has always provided wise counsel on how to best protect the American people from the threat of terrorism," Bush said in a statement. "We are safer today because of her leadership."

Townsend's job, as the president's top adviser on fighting terrorism, involved identifying terrorist groups around the globe and assessing their threat, and finding ways to track and cut off their funding. She said that experience should will be useful in the private sector as well.

Townsend -- the mother of two, ages 6 and 12 -- said she first will look into public speaking, writing and board work before pursuing opportunities in global risk management for a large multinational corporation or financial institution. Watch how Townsend is planning to use her skills »

She said she's been talking with the president about her planned departure for eight months.

Townsend's name had come up during the president's recent search for a new attorney general, but she was not considered. She said not getting the job "had absolutely nothing to do with her decision to leave."

She said Bush had wanted her to stay on in his administration.

"It was a hard decision as I have loved and will cherish my every minute of service," she said in an e-mail. "My family actually advocated that I remain and has always been supportive of my service so this was entirely my decision."

Townsend is part of the search committee to find a replacement by the beginning of next year. The president appoints the senior staff position, and it needs no Senate confirmation.E-mail to a friend